1. Field of the Invention
The present invention relates to a film for fastening cargo during transportation, and more specifically to a protective film that has a low percentage strain change, and has excellent ability to hold/fasten products. The present invention also relates to a method for fastening cargo using the film.
2. Description of the Related Art
Fastening film is used for the purpose of holding/fastening products (cargo) during transportation with a method in which the products are fastened directly in corrugated cardboard, or a method in which the products are held in a midair state sandwiched between a pair of films. Because the purpose of fastening film is to hold/fasten products during transportation, the fastening film is required to have properties such that the products are not subjected to shock and are not damaged. Moreover, fastening film is used throughout the year over a broad temperature range, and the properties in a normal temperature range in which usage is common (around 23° C.) and in a high temperature range in which the film stretches easily (above 50° C.) are particularly important.
Fastening films used from hitherto include resin films made of EVA, urethane resins and so on.
With such a fastening film, the elastic modulus and the percentage strain change are high, with the elastic modulus exceeding 60 MPa and the percentage strain change exceeding 2.0% at 23° C., and the elastic modulus being at least 20 MPa and the percentage strain change being at least 2.5% at 55° C., and hence it is difficult to stabilize products with the fastening film not fitting to the products during transportation, and thus problems arise such as the products being damaged. There are thus calls for a film having a low percentage strain change at 23° C. and 55° C.
Amid this state of affairs, a film that uses a urethane resin and is used in a state of suspension in which a computer product or the like is sandwiched in midair has been proposed (U.S. Pat. No. 6,148,591). Moreover, a film of an ethylene-styrene random copolymer has also been proposed (WO 98/10014).
However, in these patent documents, there is no mention whatsoever of the percentage strain change at certain temperatures.
The advent of a film that has a low percentage strain change at certain temperatures, preferably has a low elastic modulus, and has excellent ability to hold/fasten products during transportation is thus desired.